Page 1335 - Clinical Small Animal Internal Medicine

139 Cancer of the Heart 1273

resonance imaging (MRI) has not been shown to improve Unfortunately, cytology of the effusion is rarely diagnos­
VetBooks.ir the diagnosis of cardiac neoplasia when compared to tic as nonneoplastic reactive mesothelial cells are diffi­
cult if not impossible to cytologically differentiate from
conventional echocardiography.
Testing of the pericardial effusion tends to be of lim­
ited diagnostic utility. Cytology of hemorrhagic effusions exfoliated neoplastic mesothelial cells. Pericardial and/
or pleural biopsies are typically required for confirma­
does not reliably differentiate between neoplastic and tion of diagnosis.
nonneoplastic disease. Neoplastic effusions have been Pericardial lipomas may be diagnosed on thoracic
associated with lower pH, bicarbonate and chloride lev­ radiographs with the appearance of an adipose density
els and higher lactate, hematocrit, and urea nitrogen as within the cardiac silhouette. Echocardiography gener­
compared with serum values. Serum cardiac troponin ally reveals a homogenously echogenic mass within the
I levels have been shown to be elevated in dogs with pericardial sac with variable degrees of compression of
neoplastic pericardial effusions. the right heart chambers. Ultrasound‐guided fine needle
On necropsy, HSA appears as a red to black, blood‐filled aspiration may be attempted, although definitive diagno­
mass on the epicardium. Histopathologic confirmation is sis generally requires surgical biopsy.
rarely obtained antemortem but is marked by scattered, Cardiac myxomas, rhabdomyosarcomas and other
elongated plump neoplastic endothelial cells. By the time cardiac sarcomas require surgical biopsy for confirma­
of diagnosis, most cases have associated metastasis and tion of diagnosis.
in general HSA should be considered a systemic/dissemi­
nated disease. The clinician should always assume that
HSA is more advanced than what is evident based on Therapy
imaging modalities. Cardiac troponin I levels have not
been shown to be a reliable diagnostic screening tool. Once hemodynamically important pericardial effusion is
Definitive diagnosis requires surgical biopsy. confirmed, immediate pericardiocentesis is warranted.
Heart‐based tumors are most commonly diagnosed Ideally, an intravenous (IV) catheter is placed and a
via echocardiography. Typically, these are visualized as shock bolus of fluids is administered, but patients may
masses of mixed or homogenous echogenicity immedi­ require immediate pericardiocentesis and a IV catheter
ately adjacent to the ascending aorta, aortic arch and and fluids may need to follow.
proximal branch pulmonary arteries. Thoracic radio­ Frequently, the fluid grossly resembles port wine
graphs may show a ventral deviation of the caudal aspect which appears similar to venous blood. The presence of
of the intrathoracic trachea, resulting in a “hook‐like” dark, hemorrhagic pericardial effusion is classically
appearance if a large HBT is present. Cytologic evalua­ seen with HSA, but its presence is not pathognomonic
tion of pericardial effusion when present is rarely for HSA or other cardiac neoplasia. Less commonly,
diagnostic. Definitive diagnosis requires histopathologic the fluid may be serosanguinous from CHF or neopla­
evaluation of surgically obtained biopsies, often taken sia. Rarely, it may be grossly purulent from pericarditis.
during palliative pericardectomy. Commonly, any residual fluid will leak into the pleural
It is common for cats affected with LSA to have large cavity from the hole that has been created in the
amounts of pericardial effusion, requiring pericardio­ pericardium. Complications associated with pericar­
centesis. The pericardial effusion should be submitted diocentesis include puncture of a cardiac chamber,
for fluid analysis/cytology as lymphosarcoma may be laceration of a cardiac tumor or coronary artery with
easily diagnosed. Most often, lymphosarcoma of the subsequent intrapericardial hemorrhage. Most com­
heart produces infiltrative myocardial lesions. Echo­ monly, transient arrhythmias may occur, though they
cardiography may reveal irregular mottling and echo­ tend to be self‐ limiting and only rarely require antiar­
texture to the myocardium with focal areas of thickening, rhythmic therapy.
and concentric left ventricular hypertrophy may mimic In select cases of cardiac HSA, surgical excision may
hypertrophic cardiomyopathy. Grossly, white, pale be attempted (RA appendectomy +/‐ inflow occlusion
lesions arise from the myocardium. via right thoracotomy or median sternotomy), but in
Patients affected with pericardial mesothelioma may the majority of cases complete surgical excision is not
reveal focal thickening and irregularity of the pericardial achieveable. Pericardectomy alone is not advised due to
sac on echocardiography. However, normal pericardial the risk of exsanguination and dissemination of tumor
adipose tissue may mimic infiltrative lesions. It is very cells into the pleural cavity and has not been shown to
common to have associated pleural effusion, and the affect recurrence of clinical signs or survival. Various
presence of a modified transudate in the pleural and per­ chemotherapeutics (doxorubicin, dacarbazine, cyclophos­
icardial cavities for no obvious underlying reason should phamide, vincristine) have been attempted with a posi­
alert the clinician to the possibility of mesothelioma. tive trend in overall survival time and time to metastasis.